Often, it is desirable to compact loose particulates to remove air voids therefrom. One example is in a metal casting process in which foundry sand is compacted about a pattern to create a mold. In some cases, the pattern may be of such oomplex shape that special techniques must be used to ensure that all air voids are removed from the particulate matter and all passages and cavities in the pattern are filled. One prior method of compacting particulates about a complex pattern is disclosed in applicant's prior U.S. Pat. No. 4,456,906, assigned to the assignee of the instant application.
The above-noted patent discloses a vibratory method which utilizes an apparatus havigg vibration generators comprising horizontally mounted motors having eccentric weights thereon. The generators are operated to vibrate a bed which in turn supports a flask containing the pattern and foundry sand. Initially, the generators are operated to produce a vibratory acceleration on the mold flask and its contents in excess of the acceleration due to gravity. This acceleration causes the sand to fluidize and thus flow into and completely fill cavities in the pattern. After a short period of vibration at accelerations in excess of gravity, the stroke of the motors is reduced to reduce the acceleration to a magnitude less than the acceleration of gravity. This in turn compacts the foundry sand in place allowing it to retain its position when molten metal is subsequently introduced into the mold flask.
Certain prior compaction apparatus often permitted the horizontal and vertical component of the vibratory forces of the vibratory apparatus to be partially dissipated between the bed plate and the flask due to an unclamped coupling between the two, resulting in less than efficient compaction of material in the flask.
Other prior art devices, such as shown in U.S. Pat. No. 3,435,564 to Balz has a motor with a vertical shaft and adjustable eccentric weights on each end of the shaft. Each time the conditions of operation change, i.e. heavier parts are being handled, the apparatus has to be shut down and the eccentric weights repositioned to new locations relative to the motor shaft so as to change the operating range of the apparatus to meet the new conditions. Shut downs add costs to the finished product.